In 1995, a group of German researchers assessed sleep patterns and melatonin levels in ten patients with chronic insomnia (with a focus on sleep maintenance insomnia) and five good sleepers. Melatonin levels were found to increase earlier in insomniacs and peaked at a lower value when compared to good sleepers. The most notable disturbances in melatonin production were found in those who had the longest history of insomnia.
Because melatonin-related insomnia is especially prominent in the elderly, a 2001 study focused specifically using melatonin to treat insomnia in people 50 years and older. Melatonin treatment was found to restore sleep, and was especially effective in the middle of the night. Multiple concentrations were used in the study, but the researchers reported the best results from 0.3mg taken half an hour before bedtime.
A 2007 study from the UK also looked at using melatonin to treat insomnia in the elderly, this time focusing on prolonged-release melatonin. 354 patients participated, half of which received melatonin while the other half were given a placebo. The researchers found that treatment with prolonged-release melatonin "results in significant and clinically meaningful improvements in sleep quality, morning alertness, sleep onset latency and quality of life in primary insomnia patients aged 55 years and over." The improvement in time taken to fall asleep was comparable to that of many common sleep medications. Another study conducted the same year reported similar results, with prolonged-release melatonin significantly improving quality of sleep and levels of alertness the following morning. Side-effects were mild and rare.